This invention pertains to photographic films, and more particularly for method and apparatus for applying protective coatings to the surfaces of films, more specifically film discs. The invention is particularly adapted for use with film disc-type developing apparatus, or generally, film processing apparatus, by means of which a protective durable clear coating may be applied to the exposed surfaces of film carried on film discs.
It is known that ultraviolet curable coating materials of the kinds described in the patents of Nozari, U.S. Pat. No. 4,049,861 issued Sept. 20, 1977 and Lien et al, U.S. Pat. No. 4,156,046 issued May 22, 1979 have particular advantage as an abrasion-resistant coating for photographic films, such as for photographic color negative films popularly used in making color prints. Such protective coating materials have been marketed in the United States by Minnesota Mining and Manufacturing Company under the trade name "3M Photogard". This material applies an optically clear protective coating of approximately 2.5 microns thickness. It features high resistance to abrasion, to static electricity, to finger prints, and to a wide variety of solvents.
Also, the material has about the same index of refraction as the negative material. It prevents the growth of fungus or bacteria on the film and serves to dissipate static electricity. The coating material further tends to eliminate scratches, in that scratches are filled in and no longer are as visible when printing. Further, the coating material provides a smooth surface which reduces light scatter at the surface and enhances printability. A further advantage is that such coated films have enhanced archival characteristics in that air is excluded from the surface of the film which could deteriorate the film and the film dyes.
A particular problem exists, however, in the application of such coating materials to film discs of the kind now commonly used in film disc cameras and as disclosed in Sethi, U.S. Pat. No. 4,194,822 issued Mar. 25, 1980. The film disc has a central aperture about a plastic hub which is concentrically disposed. The hub is permanently attached to the disc and includes a keyway by which the hub can be secured to a keyed spindle for rotation during film processing. The individual films are arcuately positioned about the hub of the disc.
Film discs are commonly developed on spindles in which a plurality of the discs are stacked in side-by-side relationship for sequential application of processing fluids thereto, while the spindle is rotated. The spindle, and the film discs stacked thereon, are moved into successive baths of processing solutions, and transferred from bath to bath by appropriate arms which carry the spindle (and the discs carried thereon) to a drying station where the same films may be air dryed. For example, typical patents showing the film disc and spindle combinations include Michal, U.S. Pat. No. 4,252,430 issued Feb. 24, 1981 and Patton, U.S. Pat. No. 4,112,452 issued Sept. 5, 1978. The spindle itself has now been standardized by Eastman Kodak Company for use in its processors, and is provided to the photofinishing industry for carrying and storing up to 100 disc films. However, the apparatus which has heretofore been provided for the purpose of processing or developing film discs is not suited for the application of ultraviolet curable coatings. The application of the coating material requires the employment of certain shapes and methods which cannot be practiced by existing processing or developing equipment. First, in such coating only the film negatives should be coated. It is undesirable to coat the hub of the disc as that would be wasteful of coating, and could interfere with the proper utilization of a magnetic data storage area provided on the hub. The coating material itself is relatively expensive, while exceedingly thin film thicknesses in the range of 2 to 3 microns is ample. Further a minimum of coating material applied is desirable to prevent coating build-up, to prevent sags or ridges from forming, and to prevent interference with the definition and resolution of the image.
A further requirement is that the coated discs be subjected at the proper time to ultraviolet radiant energy for the purpose of curing. Such apparatus is not now presently available in processing or developing equipment.